Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$219.76	13.139%	$248.6343	$248.63	$248.65	$248.60
Purchase #2	$236.52	9.244%	$258.3839	$258.38	$258.40	$258.40
Purchase #3	$31.28	13.824%	$35.6041	$35.60	$35.60	$35.60
Purchase #4	$225.60	8.449%	$244.6609	$244.66	$244.65	$244.70
Purchase #5	$79.40	12.257%	$89.1321	$89.13	$89.15	$89.10
Purchase #6	$78.91	12.646%	$88.889	$88.89	$88.90	$88.90
Purchase #7	$20.63	3.612%	$21.3752	$21.38	$21.40	$21.40
7 purchase totals =	$892.10		$986.6795	$986.67	$986.75	$986.70